Treatment of hydrocarbons



Patented Mar. 14, 1939 UNITED STATES PAT ENT OFFICE 'TREATllIENT OF HYDROGARBONS No Drawing. Application July 18, 1936, Serial No. 91,425

11 Claims.

The present invention relates to the art of mineral oil refining, and has .particular reference to theseparation of crude petroleum or petroleum products into fractions of different chemical composition while of approximately'the same distillation range.

In accordance with my invention, crude petroleum or petroleum products, particularly oils of substantial viscosity, are separated into various fractions by extraction with a solvent mixture, and more particularly with a solvent mixture consisting essentially of nitrobenzene, nitrotoluene and diethylene-glycol mono-ethyl ether. In place of the glycol ether, there may be employed the alcohols such as methanol, ethanol and the like.

It is recognized in the art that mineral oils, such as petroleum, comprise essentially a mixture of hydrocarbons of various groups or homologous series of compounds, such for example, as. paraffins of the general formula CnH2n+2, olefins of the general formula CHI-i2" hydroaromatics and polymethylenes of the same empirical formula, and various other series of compounds of chain and/or ring structures in which the hydrogen to carbon ratio is less than in the foregoing series. A large number of individual compounds of each series and of differing boiling points are present in petroleum.

The various types of crude petroleum, which are generally classified into three groups, namely, parafimic base, naphthenic or asphaltic base, and mixed base, contain the various series of hydrocarbons mentioned heretofore in different proportions. For example, in the paraflinic base crude oils, such as those obtained from the oil fields of Pennsylvania, there is a relatively high proportion of hydrocarbons having a chain structure and a high hydrogen to carbon ratio, whereas. in the naphthenic or asphaltic base crude oils, there is a relatively large proportion of hydrocarbons having ring structures and a low hydrogen to carbon ratio. Mixed base crude oils, such as are obtained from the Mid-Continent oil fields, contain hydrocarbons in proportions intermediate between these two extremes.

The paraffin base oils and their distillat'es are said to be more parafiinic than the mixed base oils and their distillates and these in turn are more parafiinic than the naphthene base oils and their distillates. Conversely the naphthene base oils are more naphthenic than the mixed base oils and these in turn more naphthenic than the parafilnic base oils. The usual criteria of the degree of parafiinicity or naphthenicity of an oil are the viscosity-gravity constant and the viscosity index. The viscosity-gravity constant is a constant relating viscosity and specific gravity and is described in an article entitled The viscosity-gravity constant of petroleum lubricating oils by J. B. Hill and H. B. Coates which will be found in V01. 20, page 641 et sq., of Industrial and Engineering Chemistry. Viscous oils resulting from the distillation of Pennsylvania type crudes have viscosity-gravity constants ranging 11' from about .805 to .828, and in most instances are below .820. Those resulting from the distillation of Mid-Continent crudes have viscositygravity constants ranging from about .835 to about .855, whereas those from naphthenic crudes 15 are generally higher than .860. The viscosity index is a coefiicient based on the change of viscosity with temperature, and is described by Dean and Davis in vol. 36, page 618 of Chemical and Metallurgical Engineering. The more parafiinic 2O oils are characterized by low viscosity gravity constants and high viscosity indices, whereas the more naphthenic oils are characterized by higher viscosity-gravity constants and low viscosity indices.

My invention is based upon the discovery that oils containing both the paraiiinic series of hydrocarbons and the various naphthenic series may be fractionally extracted with a selective solvent mixture consisting essentially of nitrobenzene, 30 nitrotoluene and diethyleneglycol mono-ethyl ether. The Various series of hydrocarbons possess a differential solubility in such solvent mixture, the naphthenic hydrocarbons being much more soluble therein than the paraflinic hydro- 5 carbons. By means of extraction with such solv Vent mixture, it is possible to efiect a partial separation of the naphthenic hydrocarbons from the paraffinic, and to obtain from an oil containing both classes of hydrocarbons, an oil 40 which is much more paraffinic than the original oil and one which is much more naphthenic. By my invention, for example, it is possible to produce an oil of the quality normally obtained from Appalachian crudes, from crudes of the mixed 45 base type from the Mid-Continent area or from those of the naphthenic base type and, conversely, to obtain oils from mixed base crudes or parafiinic base crudes such as are normally obtained from. the naphthenic oils of the Gulf Coast area. In general, from oils from any source there may be obtained by my process, oils which are respectively more paraflinic and more naphthenic than the oils normally obtained from such source by distillation.

In accordance with my invention, I first mix the oil to be treated with a suitable proportion of a mixture of nitrobenzene, nitrotoluene and diethyleneglycol mono-ethyl ether at a temperature such that complete solution is effected and a homogeneous liquid obtained. I then adjust the temperature of the solution so that separation of the liquid into a two-layer system will take place. Such temperature is generally at least 35 F. below the miscibility temperature of the oil and solvent mixture. One layer will contain a relatively small amount of the solvent mixture dissolved in the parafiinicportion of the oil (raiiinate) while the other layer will contain the more naphthenic portion of the oil (extract) dissolved in the major portion of the solvent mixture. Or, I may agitate the mixture of solvents and oil at temperatures at which the same are only partially miscible, and thereby effect solution of the naphthenic portion of the oil in the solvent mixture. In either of the above procedures I may take advantage of the principles of countercur- .rent extraction.

After the extraction proper, I effect separation of the two layers which form, by any suitable procedure, as for example, by decantation. I then remove from each of the separated layers, the portion of solvent mixture which each contains, by suitable procedure, such as by vacuum distillation, thereby to obtain two oils of similar.

distillation ranges but of different chemical composition and different physical characteristics.

Before removing the solvent mixture from the undissolved or more parafiinic layer, I may add a further quantity of the solvent mixture and repeat the extraction, thereby to remove additional naphthenic constituents from said layer. The extraction step may be repeated any desired number of times, each repetition producing an oil of higher paraflinicity as evidenced by its lower viscosity-gravity constant.

A countercurrent relationship in these successive extractions may be established in the conventional manner by employing the partially spent solvent mixture containing dissolved naphthenic oil from the succeeding stages of a batchcountercurrent extraction system to extract additional quantities of oil in the preceding stages, or in a continuous countercurrent system, the oil and solvent mixture may be simply flowed in countercurrent contact with one another.

Where substantial quantities of waxy hydrocarbons belonging to the true paraffin series (CnH2n-l-2) are present, such hydrocarbons remain in the undissolved or more paraflinic layer and may cause such layer to be solid or semisolid, after the removal of the solvent mixture therefrom. In some cases, the extraction and separation of the layers may be effected at ternperatures above the melting point of the waxy hydrocarbons, so that substantial entrainment of oil in the molten or liquid wax is avoided. Such layer may be separated into solid and liquid hydrocarbons by any of the well-known dewaxing processes such as by cold-settling, filtering, or by centrifuging. In many instances it may be advantageous to dewax the oil prior to extraction. However, it is to be understood that in accordance with my invention, dewaxing may be effected either prior or subsequent to extraction;

I have found that solvent mixtures such as nitro-benzene, o-nitritoluene and diethyleneglycol mono-ethyl ether, or nitrobenzene, o-nitrotoluene and. alcohol are of particular ultility in the extraction of very naphthenic or asphaltic base hydrocarbon oils, for example, lubricating oils from California crude oil. The particular solvent mixtures mentioned above have been found to be very satisfactory when employed in the extraction of oils of widely varying characteristics and under Widely varying extraction conditions. The solvent mixtures of my invention may be employed under temperature conditions which are totally unsuitable for the use of any of the components of the mixture. For example, nitrobenzene cannot be employed at temperatures lower than about 30 F., whereas my solvent mixtures may be utilized at temperatures of the order of 5 F. or lower. On the other hand, the extraction of some oil stocks with nitrobenzene requires that the temperature be of the order of 35F. or 40 F. to produce reasonable yields of refined oil of desired characteristics. By employing my solvent mixtures-it is possible to effect satisfactory extraction of the same oil stocks at temperatures, for example, of 70 F. to 80 F., thus effecting a marked economy from the standpoint of refrigeration. In general, the solvent mixtures of my invention are more flexible, or may be of wider application, than any of the components of the mixtures used alone.

My invention will be further understood from the following specific examples:

1. An East Texas lubricating oil stock having a Saybolt Universal viscosity of 6'7 seconds at 210 F., an A. P. I. gravity of 22 at 60 F., and a viscosity-gravity constant of 0.860 was extracted in a 3-stage batch countercurrent extraction system at 5 F. with 75% by volume of a solvent mixture consisting of 56% nitrobenzene, 24% o-nitrotoluol and 20% diethyleneglycol monoethyl ether. There was produced a rafiinate oil fraction amount to 81.0% of the stock charged, such raffinate having a Saybolt Universal viscosity of 64 seconds at 210 F., an A. P. I. gravity of 252 and a viscosity-gravity constant of 0.836.

The extract oil fraction. amounted to 19.0% of.

the stock charged and had a Saybolt Universal viscosity of .158 seconds at 210 F., an A. P. I. gravity of 10.0, and a viscosity-gravity constant of 0.945.

2. A Mid-Continent lubricating oil stock having a Saybolt Universal Viscosity of 45 seconds at 210 R, an A. P. I. gravity of 260 at 60 F., and a viscosity-gravity constant of 0.846 was extracted in a B-stage batch countercurrent extraction system at 5 F. with 40% by volume of a. solvent mixture consisting of 56% nitrobenzene, 24% o-nitrotoluol and 20% diethyleneglycol mono-ethyl ether. There was produced a raftinate oil fraction amounting to 84.3% of the stock charged, such ractfinate having a Saybolt Universal viscosity of 43 seconds at 210 F., an A. P. I. gravity of 288 and a viscosity-gravity constant of 0.833. The extract oil fraction amounted to 15.7% of the stock charged and had a Saybolt Universal viscosity of 56 seconds at 210 R, an A. P. I. gravity of 115, and a viscosity-gravity constant of 0.954.

3. A Gulf Coast lubricating oil stock having a Saybolt Universal viscosity, of 198 seconds at 210 an A. P. I. gravity of 188 at 60 F., and a viscosity-gravity constant of 0.864 was extracted in a 3-stage batch countercurrent extraction system at 5 F. with 45% by volume of a solvent mixture consisting of 56% nitrobenzene, 24% o-nitrotoluol and 20% diethyleneglycol mono-ethyl ether. There was produced a raffinate oil fraction amounting to 90.7% of the stockcharged, such raffinate having a Saybolt Universal viscosity of 158 seconds at 210 F., an A. P. I. gravity of 203 and a viscosity-gravity constant of 0.856.

4. A Mid-Continent residuum oil stock having a Saybolt Universal viscosity of 143 seconds at 210 R, an A. P. I. gravity of 20.8 at 60 F., and a viscosity-gravity constant of 0.853 was extracted in a 3-stage batch countercurrent extraction system at temperatures of 70 F., 77 F., and 85 F. in the 1st, 2nd, and 3rd stages, respectively, with 250% by volume .of a solvent mixture consisting of 52.5% nitrobenzene, 22.5% o-nitrotoluol and 25% diethylene-glycol mono-ethyl ether, There was produced a raffinate oil fraction amounting to 54.1% of the stock charged, such raffinate having a Saybolt Universal viscosity of 92 seconds at 210 F., an A. P. I. gravity of 27.5 and a viscosity-gravity constant of 0.810. The extract oil fraction amounted to 45.9% of the stock charged and had a Saybolt Universal viscosity of 351 seconds at 210 F., an A. P. I. gravity of 12.7, and a viscosity-gravity constant of 0.908.

From the above examples, it will be noted that by extraction of an oil with a solvent mixture comprising nitrobenzene, nitrotoluene and diethyleneglycol mono-ethyl ether, there may be obtained oil fractions which are respectively more parafilnic and more naphthenic than the original oil. By repetition of the extraction process upon the undissolved fraction, oils of even greater parafiinicity will result. The quantity of solvent mixture to be employed will vary, depending upon the character of the solvent mixture and the stock, the temperature at which the extraction is to be carried out, and the yield and quality of refined oil desired.

While, in the above examples, I have shown the use of solvent mixtures having specific ratios of nitrobenezene to nitrotoluene and the glycol ether, I do not intend to be limited thereto, but may employ any suitable proportions of the components, depending upon the results it is desired to achieve.

My process is practically independent of the particular nature or source of the crude oil or oil fraction to be extracted. There may be produced by my process oil products of desired characteristics from oil which by distillation will not produce such products.

When, in the appended claims, oil is referred to as being viscous, it is to be understood that the oil is of substantial viscosity, i. e., of the order of 50 seconds Saybolt Universal at 100 F., or more. Likewise, herein and in the appended claims the term o-nitrotoluene is to be understood to include o-nitrotoluene and the isomers, m-nitrotoluene and p-nitrotoluene, and mixtures of the isomers containing a substantial proportion of o-nitrotoluene. The term diethyleneglycol mono-ethyl ether is to be understood to include Carbitol, which is a commercial grade of diethyleneglycol mono-ethyl ether.

What I claim is:

1. In the art of refining minerals oils, the process which comprises separating an oil containing paraffinic and naphthenic hydrocarbons into fractions respectively richer in parafiinic and naphthenic compounds by extracting said oil with a solvent mixture comprising nitrobenzene, o-nitrotoluene and diethyleneglycol mono-ethyl ether.

2. In the art of refining mineral oils, the process which comprises adding a solvent mixture comprising nitrobenzene, o-nitrotoluene and diethyleneglycol mono-ethyl ether to an oil containing paraffinic and naphthenic hydrocarbons, heating the mixture to such temperature as to effect solution, cooling the solution to form a two-layer system, and separating the upper layer from the lower layer.

3-. In the art of refining mineral oils, the process which comprises adding a solvent mixture comprising nitrobenzene, o-nitro-toluene and diethyleneglycol mono-ethyl ether to an oil containing paraffinic and naphthenic hydrocarbons, heating the mixture to such temperature as to effect solution, cooling the solution to form a twolayer system, removing the lower layer, and similarly retreating the upper layer with said solvent mixture.

4. In the art of refining mineral oils, the process which comprises bringing a mineral oil containing paraifinic and naphthenic hydrocarbons into contact with a solvent mixture comprising nitrobenzene, o-nitro-toluene and diethyleneglycol mono-ethyl ether, thereby to efiect solution of a portion richer in naphthenic hydrocarbons in the solvent mixture, separating the solution so formed from the remainder of the oil, and removing the solvent mixture from both portions of the oil, thereby to obtain fractions of the oil respectively richer in paraffinic and naphthenic hydrocarbons.

5. In the art of refining mineral oils, the process which comprises bringing a mineral oil containing paraffinic and naphthenic hydrocarbons into contact with a solvent mixture comprising nitrobenzene, o-nitro-toluene and diethyleneglycol mono-ethyl ether, thereby to efifectsolution of a portion of the oil richer in naphthenic hydrocarbons in the solvent mixture, separating the solution so formed from the remainder of the oil, and retreating the oil remaining with additional amounts of the solvent mixture.

6. In the art of refining hydrocarbon oils, the process which comprises bringing an oil containing parafiinic and naphthenic hydrocarbons into countercurrent contact with a solvent mixture comprising nitrobenzene, o-nitrotoluene and diethylene-glycol mono-ethyl ether, thereby to effect solution of a portion of the oil richer in naphthenic hydrocarbons in the solvent mixture, separating the solution so formed from the remainder of the oil and removing the solvents from the solution and the oil.

7. The method for producing parafilnic lubrieating oil from mixed base oil, which comprises bringing the oil into contact with a solvent mixture comprising nitrobenzene, o-nitrotoluene and diethyleneglycol mono-ethyl ether, thereby partially dissolving the oil, separating the solution of oil so treated, and removing the solvent mixture from the treated oil.

8. The process of treating a viscous fraction of a crude oil of one type containing paraflinic and naphthenic hydrocarbons toprocure a fraction having the quality of a corresponding fraction of a crude oil of difierent type having a greater content of paraffinic hydrocarbons, which comprises extracting the viscous fraction with a solvent mixture comprising nitrobenzene, o-nitrotoluene and diethyleneglycol mono-ethyl ether, and separating the oil so treated into portions respectively richer in paraffinic and naphthenic hydrocarbons.

9. The process of treating a viscous fraction of a mixed base crude oil to procure a fraction having the quality of a corresponding fraction of a paraffinic base crude, which comprises extracting the viscous fraction with a solvent mixture comprisstantial amounts of its naphthenic components, thereafter removing the solvent mixture and oil dissolved therein from that portion of the oil which remains undissolved, thereby to produce an oil such as is normally obtained from Pennsylvania type crude by distillation.

11. In the process of decreasing the viscositygravity constant of a viscous mineral oil, the step of extracting the oil with a solvent mixture comprising nitrobenzene;o-nitrotoluene and diethyl- 1 eneglycol mono-ethyl ether.

WILLIAM A. MYERS. 

